1. Field of the Invention
The present invention relates to rope locks that are used to secure control ropes for raising or lowering scenery sets and other equipment on theatrical stages.
2. Description of Prior Art
The theater industry uses, among others, counterweight rigging systems to raise, lower and suspend scenery sets, lighting equipment (“loads”) and other equipment that is used in theatrical productions and events. A typical counterweight rigging set consists of a balanced system of weights and pulleys by which loads can be raised and lowered. Each set is comprised of a load batten suspended from pickup cables which pass over loft block sheaves, then over a head block at one side of the stage, and finally down to a counterweight arbor. The arbor holds weights that are adjusted by the user to balance (or counterweight) the load. Movement of the load is controlled by a rope hand line that passes from the top of the arbor over the head block, down through a rope block mounted on the locking rail, around a tensioning floor block and back to the bottom of the arbor.
Rope locks used in such counterweight rigging systems fix the rope hand line in position while a load is suspended or while a load and/or counterweight is being added to or removed from the system. As a result, the rope lock must be able to fix the rope in position not only when the load and counterweight are balanced (“in-balance condition”), but also when the load and counterweight are out-of-balance (“out-of-balance condition”).
Under normal operation of the counterweight system, the rope lock can be released while the system is in balance, allowing the operator to move the load up or down by moving the rope hand line. If the rope lock is released when the system is out of balance, either the load or the counterweight may fall, potentially causing damage to equipment and injury to individuals in the area. It is therefore important that the rope lock be released only when the system is in balance.
It is known to manufacturer rope locks that include means of retaining a rope in position when a counterweight system is out of balance. Such rope locks, however, allow the handle of the rope lock to move to a release position even if the counterweight system is out of balance. Furthermore, it is difficult for an operator of such a system to determine when the system has been brought back into balance.
3. Objects and Advantages
It is therefore a principal object and advantage of the present invention to provide a rope lock with a release handle that cannot be opened when it is locking a counterweight system that is out of balance.
It is a further object and advantage of the present invention to provide a rope lock that displays an indicator when a counterweight system is out of balance.